The current series is actually the "Go" series with different subtitles each season.
Following seasons can include "Go Master" or even possibly "Go Speed" where the Yu trio finds that there are more places in space with different rules for dueling and adapt to those styles. Rush Synchro and/or Rush XYZ Summoning will be introduced in Go Rush.
With Sevens introducing Rush Fusion Summoning, it'd make sense to bring back Synchros since that was the next summoning mechanic in the original series. XYZ is most likely to appear because of how space themed both Zexal and Go Rush were. The series is not, in fact, a Distant Sequel to Sevens, but an alternate universe connected to it which takes place during the previous series' two year Time Skip.
Episode 20 heavily implies that Yudias received his red duel disk and Galaxy-type cards from Yuga, and it can be further speculated that Yuga may have encountered this universe during his time in space. This would also mean that the cast is not the descendants of the Sevens cast, but alternate dimension counterparts instead.- May or may not be jossed. Episode 39 confirms that GO RUSH takes place in a past period of SEVENS, but Yuga inventing Rush Duels in a time period before even basic Duel Monsters was invented may have whacked up the overall timeline.
The Earthdamar will continue to evolve and turn into a final boss monster.
After escaping containment from MIK, the Earthdamar gained a child like ego and the ability to possess people. However, it will turn into an adult monster by possibly possessing more people and dueling more. The Earthdamar will probably form its own physical body and become its own villain near the end of Go Rush. There is something special about Yudias that makes him different from other Kartumata.
It has been shown that the Anti-Kartumata beam doesn't work on him unlike with other Velgearians and we know for a fact that he is a Kartumata like every other Velgearian since we are shown how The Creator made him. There is also the fact that he holds the Milky Way galaxy which held a special significance for The Creator as his birthplace while Kuaidul only got the nearby Andromeda galaxy. That special difference will likely become relevant in the future of the series. The card than can revive the disappeared Velgearians is Monster Reborn.
It would fit with them being called cards that can think and Yuga's own experiences with that card could end up being part of the reason why he will show up as an obstacle. Kuaidul being able to research that card would make sense due to Otes having created Monster Reborn. If this guess is right, then there is likely much more behind that card than what we already know and that can be used to set up things for the following events that will take place in the series.